Ultrasonic testing system with variable angle transducer mount

ABSTRACT

An apparatus and method for achieving variable observations angles by a single transducer rotationally and pivotally mounted with a housing; and for utilizing the variable angle transducer to detect and trace and distance of unseen objects within a casing from the transducer by moving the transducer within its housing which is held stationary against the casing; and for determining the angle of observation between the transducer and the observed object; and thereby accurately determining the relative position and orientation of the object within the casing.

FIELD OF THE INVENTION

This invention relates generally to the field of ultrasonic testing, andmore specifically to signal transmitting equipment and methods.

BACKGROUND OF THE INVENTION

When focusing signals in ultrasonic testing, it often becomes necessaryto transmit the signal beam at an angle to the mounting surface. In theexisting prior art, angle beam transducers are manufactured at fixedwedge angles. When a change in the angle of observation (or focal point)is required, the transducers must be detached from the fixed wedge angleand reattached to the desired, different wedge angle. Multiple wedgesets must always be on hand; and, even then, the wedge angles arelimited by manufacturers to standard effective angles of, for example,30, 45, 60, 70 and 90 degrees.

SUMMARY OF THE INVENTION

Briefly described, the present invention comprises an apparatus andmethod wherein a single transducer is mounted for rotational and angularmovement within a housing to thus provide a range of varying wedgeangles without exchanging wedge elements. The apparatus of the presentinvention, in the preferred embodiment, includes a transducer searchunit mounted to a ball joint housed within a housing such that thesearch unit moves as the ball joint moves within the housing. Thetransmitter end of the search unit is immersed during operation, andthroughout its range of movement, in a fluid occupied chamber borderedat one wall by a flexible membrane.

In one embodiment of the present invention, the apparatus includes anangle determining device for determining the relative angle ofobservation, within an x-y-z coordinate system of the transducer afterthe transducer has been moved about within the housing.

One embodiment of the present invention comprises the above definedapparatus associated with a fluid conduit and valve, for ultrasonicsearching and locating of a valve element.

It is, therefore, an object of the present invention to provide a singletransducer assembly which achieves a variety of observation angles.

Another object of the present invention is to provide a transducerassembly adjustable to achieve an infinite variety of observation angleswithin a given range of angles.

Yet another object of the present invention is to provide a variableangle transducer assembly with a method and apparatus for determiningthe relative observation angle of the transducer throughout its variablearray of angles.

Still another object of the present invention is to provide a valvetesting and locating apparatus and method which utilizes an adjustableangle transducer assembly to search for, detect and determine thelocation of a valve element.

Other objects, features and advantages of the present invention willbecome apparant upon reading and understanding this specification inconjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded view of a variable angle transducer mount inaccordance with the present invention.

FIG. 2 is a partially cut-a-way side view of the mount in FIG. 1, cutalong line 2--2 of FIG. 1.

FIG. 3 is a side view of the variable angle transducer mount of FIG. 1strapped for use to a valve housing, in accordance with the presentinvention.

FIG. 4 is a pictorial view of the variable angle transducer mount ofFIG. 1, fully assembled and outfitted with a pitch angle determiningdevice, in accordance with the present invention.

FIG. 4A is an angular representation of the pitch angle determiningdevice of FIG. 4 in an x-y-z coordinate system.

FIG. 5 is a pictorial view of the variable angle transducer mount ofFIG. 1, fully assembled and outfitted with a pitch angle determiningdevice of an alternate embodiment to that of FIG. 4.

FIG. 5A is an angular representation of the pitch angle determiningdevice of FIG. 5 in a x-y-z coordinate system.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now in greater detail to the drawings, in which like numeralsrepresent like components throughout the several views, the presentinvention is seen as comprising a variable angle transducer mount 10shown in exploded detail in FIG. 1. The transducer mount 10 comprises ahousing 12 formed with a large cylindrical central channel 14, a flattop rim 15, flat bottom rim 16 and an outer wall 18. The outer wall 18defines an upper segment which is wider in cross-section (see FIG. 2)than the bottom rim 16, and a tapered, lower segment 20. At the bottomrim 16, a circular ledge 25 is formed protruding into the centralchannel 14. Three, parallel, internally threaded bores 23 extend fromthe top rim 15, through the upper wall segment 19 and break the surfaceof the housing 12 through the tapered, lower segment 20. A threaded pin24 occupies the bottom end of each of the bores 23, and protrudes fromthe tapered wall segment 20. The amount of protrusion of the pins 24 isadjustable by virtue of the threaded nature of the bores 23 and pins 24.Two strap holding pins 27 are mounted at the upper wall segment 19. Thehousing 12 is also formed with a threaded screw hole 28 extendinggenerally perpendicular to the cylindrical axis 31 of the centralchannel 14, from the outer wall 18 through the upper segment 19 and intothe central channel 14. A flat-end screw 29 occupies this screw hole 28and is of sufficient length to extend from the outer wall 18 to thecentral channel 14. An eyelet 30 is bolted to the upper wall segment 19;but its bolt portion does not extend into the central channel 14.

A disk shaped membrane 34, of diameter greater than the inside diameterof the circular ledge 25 is placed in the central channel 14, resting onthe circular ledge 25. A spacing washer 35 is set on top of the membrane34 and is supported by the circular ledge 25, thus sandwiching theperipheral edge of the membrane between the washer and the circularledge. A ball joint assembly 42 is set into the central channel 14 atopthe washer 35. The ball joint assembly includes a rim segment 44 and aball segment 45. The rim segment 44 includes a cylindrical outer wall 47of diameter, preferrably, only slightly less than the inside diameter ofthe central channel 14. The rim segment 44 also includes an innerpassage 48 formed to accept the ball segment 45 in a manner typical toball joint assemblies. The ball segment 45 is mounted in the innerpassage 48 and enjoys complete rotational and pivotal freedom within therim segment 44, as is typical of ball joint assemblies. The ball segment45 is provided with a central, cylindrical passage 50 extendingcompletely through the center of the ball segment. A threaded element 52is press-fitted into the cylindrical passage 50 of the ball segment 45.A hole 46 is drilled through the rim segment 44 perpendicular to thecylindrical axis of the outer wall 47 and extending from the outer wall47 through to the inner passage 48. The hole 46 is filled with a plug 49which, preferrably, extends the full length of the hole. In preferredembodiments, the plug is formed of brass. When the ball joint assembly42 is set into the housing channel 14, the hole 46 of the rim segment 44is aligned with the threaded screw hole 28 in the housing.

A clamp plate 55 is set on the top rim 15 of the housing 12. The clampplate 55 is formed with a central opening 56. In the disclosdembodiment, the central opening 56 is circular, having an insidediameter which is less than the inside diameter of the central channel14 of the housing 12. The inside diameter of the opening 56 issufficiently large to avoid contact with the ball segment 45 as itpivots in the rim segment 44 of the ball joint assembly 42. The clampplate 55 is held to the rim 15 of the housing 12 by screws 58 extendinginto the threaded bores 23 of the housing 12. As seen, the screws 58occupy the same bores 23 as the threaded pins 24.

Once the above mentioned elements are all in place, it is seen that achamber 62 is formed above the membrane 34. This chamber 62 is accessedthrough the passage 50 in the ball segment 45. A couplant material 63 isplaced in the chamber 62 through the passage 50. In the preferredembodiment, the circular ledge 25, membrane 34, washer 35 and rimsegment 44 of the ball joint assembly 42 define a combined height whichis equal to or slightly greater than the full height of the housingchannel 14. Thus, as the clamp plate 55 is screwed down onto the housingrim 15, it presses the rim segment 44, washer 35 and membrane 34, as aclamp, against the circular ledge 25; thereby creating a seal at themembrane 34 preventing leakage of the couplant 62. A transducer searchunit 70 is held within the cylindrical passage 50 of the ball segment45. The search unit 70 is of a type known in the industry, including anelongated, cylindrical body 71, a signal head 72 and a connector end 73.The otherwise typical search unit 70 is, for purposes of the presentinvention, formed with a threaded segment 74 along the head end of itsbody 71. A signal carrying cable 80 is connected by matching cableconnector 81 to the search unit connector end 73. The cable 80 extendsto the signal generating and recording unit 82 of a type known in theindustry. The search unit 70 is held within the ball segment 45 bythreading the threaded segment 74 of the search unit into the threadedelement 52 of the ball passage 50. In the preferred embodiments, thesearch unit is seated far enough into the threaded element 52 and thereis sufficient couplant material 63 within the chamber 62 such that thesignal head 72 is, at all time, immersed in couplant material 63.

It can be seen that, as the ball segment 45 rotates and pivots withinthe rim segment 44, the search unit 70 rotates and pivots with the ballsegment. Whereas, prior to seating of the search unit 70 in the ballsegment 45, the ball segment enjoyed complete and unlimited rotationaland pivotal movement within the rim segment 44, such unlimited movementis now restricted by the protruding search unit body 71. Nonetheless,the combination search unit 70 - ball segment 45 continues to enjoycomplete 360° rotational freedom about the cylindrical axis 31 of thecentral channel 14 (as depicted by arrows "φ"), and enjoys at leastlimited angular (pivotal) movement from the axis 31 (as depicted byarrows "α"). See FIG. 2. It is noted that the washer 35 is ofsufficiently large inside diameter to avoid possible binding of the ballsegment 45 by the washer 35 as the ball segment rotates and pivots.Furthermore, in the preferred embodiment, the washer 35 is of sufficientheight to act as a spacer between the membrane 34 and ball segment 45which prevents striking of the membrane by the ball segment 45 or by thehead 72 of the search unit 70 as the ball and search unit rotate andpivot.

FIG. 3 depicts the variable angle transducer mount 10 mounted for use,in one of its preferred applications, upon a valve body 85. In a moregeneral sense, the valve body 85 will sometimes be referred to as thefluid conduit 85. In such an application, the transducer mount 10 ismoved manually about the conduit 85 to a location which the user deemspractical (based upon the contour of the valve body/conduit 85) fortransmitting a signal to the generally anticipated location of a valveelement 86 within the valve body 85. A couplant paste 89 is liberallysmeared on the conduit 85 at the location where the transducer mount 10is to be placed. The transducer mount 10 is placed against the conduit85 with its membrane 34 being immersed in the coupling paste 89 and thebottom rim 16 and membrane 34 as close as practicable to the conduitsurface - touching if possible. In the preferred embodiment, themembrane 34 is flexible and the membrane contacts the conduit 85 surfaceand takes on the contour of the conduit. The transducer housing 12 isheld stationary on the conduit. The transducer housing 12 is heldstationary connected to the strap holding pins 27 of the transducerhousing 12 and encircling the valve body 85. Assisting in holding thetransducer housing 12 in place are the threaded pins 24 which protrudefrom the lower wall segment 20 of the housing 12. These pins 24 arepointed at their ends and act as "contact feet" which assist inminimizing the skidding or sliding of the housing 12 along the conduit85. It is noted that the pins 24 are adjustable and protrude only farenough to make contact with the conduit 85 without unnecessarily liftingthe bottom rim 16 and membrane 34 away from the conduit surface. Alsoassisting in maintaining the housing 12 in place is a tie down string 92which, as shown, is connected to the eyelet 30 and tied to anappropriate object to cooperate with the contact feet 24 in counteringslippage and skidding of the housing along the conduit surface.

With the transducer housing 12 in place, the user begins sending anultrasonic signal 94 (also referred to herein as a sound wave or signalbeam) from the head 72 of the search unit 70. The transmission ofsignals is done in a manner known in the industry; and, in the preferredembodiments a "pitch and catch" technique is used in a manner known inthe art to "view" the objects (i.e. valve elements 86) of the valve body85. In search of the valve element 86 within the valve body 85, the userrotates and pivots the search unit 70 within the limits of the freedomof movement provided by the transducer mount 10 design as expressedabove. The pivoting and rotating of the search unit 70 is accomplishedwithout moving the housing 12 and signals 94 are sent from all thevarious positions of the search unit 70 and received and analyzed. Oncethe user has satisfied himself/herself that the object (i.e. valve 86)being sought has been located, or has otherwise satisfiedhimself/herself as to the search unit 70 position, the search unit islocked in that position. The position is locked by turning the flat-endscrew 29 to screw it further into the screw hole 28 until the flat endof the screw contacts the plug 49 in the rim segment 44 of the balljoint assembly 42. Continued insertion of the screw 29 pushes the plug49 along the hole 46 until it is pressed against the outer surface ofthe ball segment 45, thus binding the ball segment and preventingfurther movement. In the preferred embodiment, as mentioned above, theplug 49 is made of brass, in an effort to prevent its scratching of thehighly polished surface of the ball segment 45.

The signal generating and recording unit 82 provides the electricalpulse required by the transducer search unit 70 and also collects andrecords new resultant, returned signals, converting them to time anddistance values, all in a manner known in the industry. Thus, a distancevalue of the observed valve element 86 segment from the transducer head72 is provided.

It can be seen that it is possible to determine the distance from thesearch unit head 72 of the segment of the valve element 86 being "lookedat" by the search unit 70. This determination is made in accordance withprinciples of ultrasonic testing. It now becomes necessary to determinethe direction of the observed segment of the valve element 86 from thesearch unit head 72, in order to accurately determine the location of asegment of the valve element. In order to establish the relativedirection of the observed valve 86 segment from the search unit head 72,the preferred embodiment of the present invention determines therelative angle of the center line 95 of the signal beam 94 with respectto the x-y-z planes. The center line 95 of the signal beam will, also,be referred to herein as the "observation axis" 95. This relative angleof the observation axis 95 to the x-y-z planes shall be referred to asthe "pitch angle".

In accordance with one, preferred embodiment of the present invention,the pitch angle is determined through use of a pitch angle device 97 asseen in FIG. 4. The pitch angle device 97 comprises a cable connectoradaptor 98 which allows for access of the signal cable 80 at a rightangle to the search connector end 73. (See FIG. 4) Welded or otherwiseattached to the connector adaptor 98 is a first post member 100. Thefirst post member 100 is attached so as to extend parallel to thecentral axis of the search unit body 71 when the connector adaptor 98 isattached to the connector end 73 of the search unit 70. In the preferredembodiment disclosed hereby, the central axis of the search unit body 71is colinear with the centerline 95 of the signal beam 94. The postmember 100 is formed with a swivel joint 101 at its free end. Alsomounted at the free end of the post member 100 is a first protractordevice 102 which is semicircular in profile and includes angular indicia103 along its outer edge in the manner of a typical protractor. Thefirst protractor device 102 is fixedly mounted to the first post member100. Connected to the swivel joint 100 and hanging from the first postmember 100 is a second post member 104. This second post member 104swivels freely within the swivel joint 101 and, thus, acts like a "plumline" in that it always seeks a vertical orientation. A thumb screw 99at the swivel joint 101 is used to lock the relative movement betweenthe first post member 100 and the second post member 104 once thevertical orientation of post 104 has been achieved. The second postmember 104 is formed with a sight hole 105 from which the indicia 103 ofthe first protractor device 102 can be viewed. The sight hole 105includes centerline markings 106 which represent the centerline of thepost member 104 and, thus, the vertical axis. Fixedly attached to thelower end of the second post member 104 is a second protractor device109 which is generally disk shaped. This second protractor device 109defines a plane which is, in the preferred embodiment, perdendicular tothe centerline of the second post member 104. The second protractordevice 109 includes angular indicia 110 along its outer edge in themanner of a typical protractor. The diameter 111 which includes thereference (or zero degree) point is seen as being permanently orientedwithin the same plane as in the centerline 95 of the first post member100, and thus the centerline of the observation axis 95. A third postmember 114 (also referred to as the pivot post 114) is pivotallyconnected to the bottom of the disk protractor 109. The pivot post 114is connected at the center point of the disk protractor 109 in orderthat it may pivot 360° about the centerline 106 of the second postmember 104. During use, the pivot post 114 is used to represent aselected horizontal axis (Z axis). A centerline indicator mark 115 onthe pivot post 114 represents the centerline of that post. A secondthumb screw (not seen) at the connection between the pivot post 114 andthe second post member 104 locks the pivot post relative to the secondpost member when desired.

Thus, in operation, it can be seen that the pitch angle device 97 isutilized to establish the pitch angle of the observation axis 95 asfollows: the first post member 100 is attached to the transducer searchunit body 71 and, thus, represents the observation axis 95; the angle ofthe observation axis 95 with respect to the vertical axis (Y axis) 106is read at the sight hole 105 from the first protractor device 102 andis called the "inclination angle (); the pivot post 114 is pivoted toalign parallel with a chosen horizontal axis (Z axis), also called thereference Z axis (Z_(r)) - for example, in the disclosed valve elementdetecting application of FIG. 3, the reference Z axis lies within avertical plane parallel to the direction of fluid flow "F"; the angle ofthe observation axis 95 with respect to the chosen Z axis is read fromthe disk protractor 109 at the pivot post indicator mark 115 and thisangle is referred to as the "plane angle" (ρ); and, finally, the pitchangle (PA) is calculated by the following formula:

    PA=INVTAN (COSρ-TAN )

After having acquired the distance value utilizing the ultrasonictransducer and the pitch angle using the pitch angle device, the user isnow able to locate the observed segment of the valve element 86 (orother observed object). By now loosening the flat-end screw 29 to againfree the ball segment 45 for movement, the user pivots and rotates thetransducer search unit 70 to observe yet another segment of the valveelement 86. By repeating the steps mentioned above, the user canestablish a distance and pitch angle for numerous segments of the valveelement 86, thus creating a trace of the valve element 86 to accuratelyestablish the orientation and position of the valve within the valvebody 85. These distance and angle measurements can be translated to twoand three dimensional drawings in order to give interested parties a"picture" of the valve element 86 within the valve body 85. It isunderstood that there is the possibility of circumstances where thefluid conduit 85 will itself be tilted so that the direction of fluidflow "F" is not within a horizontal plane. In such a situation,transferring of pitch angle measurements to a two or three dimensionaldrawing will be facilated by modifying the pitch angle to compensate forthe tilt of the valve body 85. This is accomplished by acquiring areading of the inclination angle of the valve body 85; that is, theangle of inclination of the fluid flow "F" with respect to the veritcalaxis (Y axis) is determined and substracted from the angle ofinclination first established above and substituting this remainder asthe angle of inclination in the above mentioned equation for pitchangle.

An alternate embodiment of the pitch angle device 97 is seen in FIG. 5.In this alternate embodiment, the first protractor device 102' isfixedly mounted to the top edge of the first post member 100. The secondpost member 104' includes an extension arm 107 which is a part of andmoves with the second post member 104'. The extension arm reaches theindicia 103' of the first protractor device 102' where its head end 108bears a centerline marking 106' which represents the centerline of thepost member 104' and, thus, the vertical axis. The second protractordevice 109', of the embodiment of FIG. 5, is pivotally connected to thebottom of the second post member 104'. This disc protractor 109' isconnected with its centerpoint at the centerline of the second postmember 104' in order that the disc 109' rotates 360° about thecenterline of the second post member 104'. The third post member 114'is, in this embodiment, fixedly attached to the disc protractor 109'with the centerline of the third post member lying parallel to andcoplaner with the reference diameter 111' of the disc protractor. A leg116 is fixedly attached to the second post member 104' and defines apointer 117 at its free end. The leg 116 is of such length andorientation that the pointer 117 is located slightly above the discprotractor 109' and adjacent the indicia 110' of the disc. The pointer117 is permanently positioned within the same plane as the centerline 95of the first post member 100, and thus the centerline of the observationaxis 95. The pitch angle device of FIG. 5 functions similarly to that ofFIG. 4. However, in this embodiment, as the pivot post 114' is pivotedto align with the reference Z axis, the disc protractor also pivots(rotates). Thus, the plane angle (ρ) is read at the leg pointer 117. Theinclination angle () is read at the centerline marking 106' on theextension head 108.

In alternate embodiments of the present invention wherein the variableangle transducer mount 10 is to be utilized in high temperatureenvironments, a lubricant comprising graphite occupies the joint betweenthe ball segment 45 and rim segment 44 of the ball joint segment 42. Inpreferred embodiments of the present invention, the couplant material 63is a fluid couplant, chosen from existing couplants, which has a boilingpoint exceeding the maximum operating temperature, maintains arelatively stable volume over the operating temperature range, is a goodtransmitter of sound, is non-destructive to the exposed transducer head72 and is of sufficiently high viscosity to prevent leakage through theball joint assembly 42. The membrane 34 of preferred embodiments ischaracterized in that it has low attenuation properties, withstandstemperatures within the operating temperature range, has sufficientlylow porosity to prevent leakage or passage of the couplant material, anddoes not react with the couplant material 63 or the couplant paste 89.An example of such membrane is a silicone rubber of, for example, 0.030inch thickness.

In alternate embodiments of the present invention, the clamp plate 55provides an additional function as a template. That is, the centralopening 56 of the clamp plate 55 is varied in shape and diameter todefine an outer range of pivotal movement (i.e. angle "α"). Thethickness of the clamp plate 55 at the location of the central opening56 is also varied to assist in this template function. Without limitingthe purpose of this template, it can be seen that the template is usedto prevent the observation axis 95 from striking the surface of thevalve housing 85 at an angle which exceeds the allowable critical anglefor the particular metal from which the conduit 85 is fabricated.

In an alternate embodiment of the transducer mount 10 of the presentinvention, the membrane 34 is not present. In this embodiment, thespacing washer 35 is retained to maintain the ball joint assembly 42 aselected distance away from the bottom rim 16 of the housing 12. In thisway, as the rim 16 is placed in contact with the valve body 85 or othercasing, the ball segment 45 and transducer head 72 will not strike thevalve body as the ball segment and transducer search unit 70 are rotatedand pivoted within the housing 12. In this alternate embodiment, theuser must be carefull to maintain a continuous supply of couplant pasteand/or fluid or other couplant material between the transducer head 72and the valve body 85 in order that the ultrasonic sound signal 94 isnot transmitted through air.

It is understood that the valve housing application of FIG. 1 is onlyone application of the apparatus and method of the present invention.The present invention is not to be limited by the specifics of thedisclosed application. Rather, the valve body/conduit 85 and valve 86are representative of casings and observed objects, respectfully,encountered in other applications.

Furthermore, whereas the present invention has been described in detailwith specific reference to preferred embodiments and applicationsthereof, it will be understood that variations and modifications can beeffected within the spirit and scope of the invention as describedbefore and as defined in the appended claims.

We claim:
 1. Method of searching for, detecting and locating a valveelement within a fluid conduit, said method comprising the stepsof:mounting a transducer search unit for rotational and angular movementwithin a housing; immersing the transmitter head of the search unit in afluid couplant within the housing; holding the housing stationaryagainst the fluid conduit; repeatedly transmitting a signal beam fromthe search unit into the conduit in search of the valve element andreceiving the reflected beam; rotating and pivoting the search unitwithin the housing while repeatedly transmitting the signal beam;detecting the valve element with the signal beam; measuring theinclination angle between the centerline of the signal beam and thevertical axis; measuring the plane angle between the centerline of thesignal beam and the direction of fluid flow through the conduit at thevalve; and calculating the location of the valve element relative to thetransmitter head.
 2. Method of claim 1, wherein the step of calculatingthe location of the valve element relative to the transmitter headcomprises the steps of:determining the distance traveled by the signalbeam from the transmitter head to the valve element; calculating thepitch angle of the centerline of the signal beam utilizing the formula:Pitch angle equals the inverse tangent of the difference of the cosineof the plane angle minus the tangent of the inclination angle; andestablishing the location of the valve element at the determineddistance from the transmitter head along the calculated pitch angle. 3.Method of searching for, detecting and locating an object within acasing, said method comprising the steps of:mounting a transducer searchunit for rotational and angular movement within a housing; immersing thetransmitter head of the search unit in a fluid couplant; holding thehousing stationary against the casing; repeatedly transmitting a signalbeam from the search unit into the casing in search of the object andreceiving the reflected beam; rotating and pivoting the search unitwithin the housing while repeatedly transmitting the signal beam;detecting at least a segment of the object with the signal beam;measuring the inclination angle between the centerline of the signalbeam and the vertical axis; measuring the plane angle between thecenterline of the signal beam and a reference Z-axis; and calculatingthe location of the segment of the object relative to the transmitterhead.
 4. Method of claim 3, wherein the step of calculating the locationof the segment of the object relative to the transmitter head comprisesthe steps of:determining the distance traveled by the signal beam fromthe transmitter head to the object segment; calculating the pitch angleof the centerline of the signal beam utilizing the formula: Pitch angleequals the inverse tangent of the difference of the cosine of the planeangle minus the tangent of the inclination angle; and establishing thelocation of the object segment at the determined distance from thetransmitter head along the calculated pitch angle.
 5. Method of claim 4,further comprising the step of maintaining the housing stationaryagainst the casing while repeating a plurality of times in sequence thesteps of rotating and pivoting the search unit within the housing whilerepeatedly transmitting the signal beam, detecting a segment of theobject with the signal beam, measuring the inclination angle, measuringthe plane angle, and calculating the location of the detected objectsegment relative to the transmitter head to trace at least a largeportion of the object.
 6. Method of claim 5, further comprising the stepof providing a representative drawing depicting the relative positionsof the traced portion of the object, the casing and the transducer head.